The distinctive characteristics of the populations of Parodia scopa (Sprengel) N. P. Taylor living in the Quebradas of Treinta y Tres Department, in Uruguay, known as Notocactus scopa var. marchesi W. R. Abraham or Parodia scopa ssp. marchesi (W. R. Abraham) Hofacker, consist of a smaller number of ribs (23-28), always within the range of the species (25-40), and whitish central spines (Hunt et al. 2006, text: 223; atlas: 315, pl. 315.1), sometimes yellowish (Gerloff et al. 1995: 78), as confirmed by our investigations (see photo). Even this feature does not appear to be exclusive of populations to Trenta y Tres, since other groups of P. scopa living in Rio Grande do Sul (Brazil) are described with white central spines, such as Notocactus scopa var. ramosus (Osten) Backeberg, (white to dark brown) (Gerloff et al. 1995, 79), yellow as Notocactus scopa var. daenikerianus Krainz (from yellow to honey-colored), or like Notocactus scopa var. glauserianus Krainz, from orange to brownish yellow (Backeberg 1966 / en. ed. 1977, 348). For these reasons, besides the fact that no other factor distinguishes it from the other populations of P. scopa, if not a relative geographical isolation (even included in the territorial area of the species), we consider the marchesi form not so defined to assume the rank of species; and we believe that the taxa that have been considered till now at infraspecific level are synonyms of P. scopa. (October 2010)

Parodia scopa (Sprengel) N. P. Taylor is a taxon with numerous and variable populations, but with a rather fragmented distribution. In contrast, the other dominant species of the genus Parodia Spegazzini of the Pampa Biome, i.e. Parodia erinacea (Haworth) N. P. Taylor as we conceived (Anceschi & Magli 2012b, 26-33), Parodia mammulosa (Lemaire) N. P. Taylor and Parodia ottonis (Lehmann) N. P. Taylor (whose populations we also refer to in the note on Parodia oxycostata (Buining & Bederoo) Hofacker), in addition to populations numerous and variable in shape, manifest a certain spatial continuity. On the diversity in the spination of the various populations of P. scopa, and on the substantial uniformity of forms of growth, we have already expressed our position in the study on the marchesii populations living in Uruguay, in the quebradas of the Depto of Trenta y Trés (Anceschi e Magli 2010, 28; A&M 294, photos 10-25). A similar situation occurs in Brazil, in the northern part of the range of P. scopa. Among the rocky outcrops (serras and coxilhas) of the Pampa Biome, in the centre-south of the Rio Grande do Sul, below the BR 290, which bisects the state from east to west. Even here, several populations of P. scopa occupy the territory distinguishing themselves essentially only by their spination. In fact, as we will see, in the case of Parodia rudibuenekeri (W. R. Abraham) Hofacker & P. J. Braun, forms and distribution areas are not so distinct. To the southwest of São Gabriel populations of Parodia succinea (F. Ritter) N. P. Taylor are living (A&M 787, photos 26-58), which quietly can be assimilated by the forms with clear spines of P. scopa. In fact, all the characters of the first taxon are included, or merged, with those of the second. In addition, the form of growth is typical of the taxon (A&M 55, photos 01-05; A&M 294, photos 10-25, A&M 787, photos 26-58; A&M 79, photos 59-83; A&M 793, photos 84-104). But while P. succinea is considered, in the latter literature, to be a subspecies of P. scopa (Hunt 1999a, 253; Anderson 2001, 552-553; 2005; 2011; Hunt et al. 2006, text: 223), in contrast Parodia rudibuenekeri (W. R. Abraham) Hofacker & P. J. Braun was recognized at the rank of species (Hunt 1999a, 252; Anderson 2001, 551; 2005; 2011; Hunt et al. 2006, text: 223). Reto Nyffeler in "Further referrals of 'limbo' species" in CCC1 (1997, 4: 9), had already correctly identified Notocactus rudibuenekeri W. R. Abraham as a synonym of P. scopa. Then in "Nomenclatural adjustments in Parodia" Hofacker & Braun (1998, 6: 10) published P. rudibuenekeri, which is the text in full:

Parodia rudibuenekeri (Abraham) Hofacker & P. J. Braun comb. nov. Basionym: Notocactus rudibuenekeri Abraham, Succulenta 67 (6): 133-138 (1988). Comment: P. rudibuenekeri and P. scopa grow about 1 km apart at Pedra do Segredo (Brazil: Rio Grande do Sul). It is to be expected that there are points of contact. There are differences in various markings such as spination and flower. No hybrids or intermediates are known. Seed-grown plants always show the distinctive markings of their parents [A.H.].

The two taxa live really very close, in the area of Caçapava do Sul, Rio Grande do Sul (BR). Precisely on the rocky outcrops of sandstone conglomerates of the formation Pedra do Segredo. On one of these, the Pedra da Abelha, lives the population of P. rudibuenekeri; while on the surrounding outcrops, including the nearby Pedra do Segredo (about 1.5 km as the crow flies), are living populations of P. scopa. The character that distinguishes the rudibuenekeri population from the scopa populations, is basically the colour of the spines: completely white for the first, with the centrals red-orange for the other. Given the morphological and spatial proximity of the two taxa and, as also Hofacker does not exclude, between the two populations there are points of contact, which we prefer to define as melting points. During the last surveys in the area (2011), we found, in discrete areas of the habitat, populations where there are the two forms. At the Pedra do Leão, another of the outcrops of the formation, in the same population (A&M 79, photos 59-83) coexist: Individuals with 4 central spines variegated in reddish yellow, and all radial white (photos 59-62), individuals with all white spines (photos 68-70), individuals with central spines orange-red and white radials (photos 71-74), and groups where individuals with completely white spines and others with red orange centrals (photo 78-79) co-exist side by side. It should be noted that even among the individuals of the Pedra da Abelha (rudibuenekeri population), can be observed central spines variegated in reddish yellow (A&M 793, photo 94), as between those of Pedra do Leão (photo 52). As pointed out for P. succinea, also P. rudibuenekeri shows the typical growth form of the stems of P. scopa. Regarding Hofacker‘s assertion "Seed-grown plants always show the distinctive markings of their parents", we emphasize that phyletic distinctions on such similar taxa, based on morphological features of a few pot-grown plants, are likely to bring us back to a typological, and not biological, concept of species. Following the foregoing, as the populations of marchesii from Uruguay, also P. succinea and P. rudibuenekeri are to be considered populations, with clear spines, not taxonomically distinguishable in the range of P. scopa. We recall that the other taxon connected by the recent literature (Hunt 1999a, 253; Anderson 2001, 552-553; 2005; 2011; Hunt et al. 2006, text: 223) to P. scopa, always following a Hofacker‘s proposal (1998, 6, 10), namely Parodia scopa ssp. neobuenekeri (F. Ritter) Hofacker & P. J. Braun, is instead the only one that clearly shows that it does not belong to this phyletic line, i.e. because of the distinct form of growth. Smaller stems and more compact with each other, forming large groups (A&M 261, photo 1-14; A&M 796, photo 15-28). For this reason, we recognize it at the species level in the genus Parodia Spegazzini, Parodia neobuenekeri(F. Ritter) Anceschi & Magli (Anceschi & Magli 2010, 33), the taxon living between Minas de Camaquã and Santana da Boavista. (June 2013)